Field of the Invention
The present invention relates to a differential device which distributively transmits rotational force of a differential case to a pair of output shafts.
Description of the Related Art
Japanese Patent Application KOKAI Publication No. 2014-190374, for example, has made known a differential device which distributively transmits rotational force of a differential case to a pair of output shafts, comprising: a pinion (differential gear) placed in the differential case; a pinion shaft (differential gear support portion) supported in the differential case and penetrating through and rotatably supporting the pinion; and a pair of side gears (output gears) including at respective outer peripheral portions thereof gear portions which are placed in mesh with the pinion, the side gears facing each other with the pinion shaft interposed therebetween and being connected respectively to the pair of output shafts, wherein, conventionally, for example, an oil reserving portion is provided in a portion where the pinion and the pinion shaft face each other such that the oil reserving portion faces a space adjacent to an end surface of the pinion that is located on a radially inner side of the side gears, and lubricant oil is introduced to mutually-facing surfaces of the pair of side gears via a lubricant oil supply passage provided between inner peripheral shaft portions of the side gears and the output shafts and then part of the introduced lubricant oil can be supplied to the oil reserving portion.
In the conventional device, however, the lubricant oil introduced into an interstice between the mutually-facing surfaces of the pair of side gears tends to flow outward in the radial direction along the mutually-facing surfaces due to centrifugal force. As a result, most of the introduced lubricant oil flows directly toward the gear portions in outer peripheries of the side gears continuous to the mutually-facing surfaces. For this reason, an effect of lubricating meshing portions of the side gears and the pinion can be sufficiently obtained. On the other hand, however, an amount of lubricant oil supplied to the oil reserving portion is relatively small. This arises a problem that an effect of lubricating a fitting portion, that is, a rotation sliding portion, between the pinion and the pinion shaft cannot be sufficiently obtained.
In addition, the problem of the insufficient lubrication of the rotation sliding portion between the pinion and the pinion shaft may be more conspicuous particularly under severe driving conditions with high-speed rotation of the pinion as in a case, for example, where a width of the differential case is reduced in an axial direction of the output shafts by making a diameter of each side gear sufficiently larger than a diameter of the pinion so that the number of teeth of the side gear can be set sufficiently larger than the number of teeth of the pinion.